China's non-manufacturing sector expanded at its fastest pace since June 2014 in September, official data showed Saturday.

The sector's business activity index, sometimes called the non-manufacturing purchasing managers' index (PMI), rose to 55.4 in September from 53.4 in August, according to the National Bureau of Statistics (NBS).

A reading above 50 indicates expansion, while a reading below that reflects contraction.

"The growth momentum for the non-manufacturing sector has become stronger," said NBS senior statistician Zhao Qinghe.

As a major part of the non-manufacturing sector, the service industry's business activity index rose from 52.6 in August to 54.4 this month.

Driven by strong manufacturing expansion, the index for production-related services rose from 54.6 in August to 59.7.

NBS data showed that manufacturing PMI stood at 52.4 in September, the fastest expansion since May 2012.

Entering a peak season for construction, the business activity index for the construction industry rose from 58 to 61.1.

The sub-index for new orders rose from 50.9 in August to 52.3 this month, indicating faster expansion of market demand, while that for business outlook rose to 61.7 from 61, staying above 60 for a fifth month.

Other sub-indices rose across the board, including those for sales prices, employees and export orders.